The invention relates to a runflat system for a motor vehicle, such a system enabling the vehicle to travel a considerable distance at relatively high speed with a tubeless tire that is partially or totally deflated.
In general, for fitting to civilian vehicles, runflat devices must be suitable for mounting on standard wheel rims, i.e. on one-piece rims having a drop center.
Presently known runflat devices are generally constituted by a ring which is mounted tightly around the wheel rim inside the tire. The ring is either made as a relatively flexible single piece from which a slice has been removed, or else of at least two circularly arcuate rigid pieces or xe2x80x9csectorsxe2x80x9d. To enable the ring to be mounted tightly against the rim, it is necessary to provide assembly and clamping fasteners between the facing ends of the ring sectors. The assembly and clamping fasteners are rigid and constituted by mechanical elements such as nuts and bolts, for example.
Unfortunately, experience shows that rigid fasteners constitute the weak link in runflat devices (e.g. due to fatigue phenomena). Furthermore, mounting a runflat device is an operation that requires the operator to be specially trained in particular because of the small amount of space available for receiving the tool required for clamping the ring on the rim.
In document FR-97/13618 in the name of the Applicant, the runflat device is constituted in such a manner as to eliminate assembly and clamping fasteners. It comprises at least one open inner ring of relatively rigid material for mounting on the rim, and a substantially inextensible continuous outer ring engaged on the inner ring so as to clamp it and fix it on the rim.
In an improvement proposed in document FR-98/04225, also in the name of the Applicant, the ring is made up of three parts, namely:
two first annular parts that are open via respective slices and that are designed to be mounted one on the other around the rim; and
a third annular part that is continuous and coaxial with the above two parts, said third part serving to clamp the resulting system on the rim.
Runflat devices are also known which are designed to be mounted on non-standard rims made up of two portions, and in which the means for fixing together the two portions of the rim are also used for fixing the sectors of the ring.
An object of the invention is likewise to avoid the use of assembly and clamping fasteners between the sectors of a runflat ring on a one-piece non-standard rim.
To this end, the invention provides a runflat system for a motor vehicle, the system comprising a non-standard one-piece rim having at least a first peripheral cavity or drop center to enable a tire to be mounted on the rim, and a runflat device for mounting on the rim inside the tire, the device being constituted by a rigid ring split into at least two circularly arcuate elements or sectors, wherein the rim presents at least one second peripheral cavity which is separated from the first cavity by an intermediate peripheral ridge, wherein each sector of the ring presents a radially inner portion for being received in the second cavity, and wherein the system also has means for fixing the sectors in the second rim cavity.
According to another characteristic of the invention, the means for fixing the ring sectors on the rim comprise first means for taking up lateral forces tending to move the sectors laterally inside the second cavity.
Advantageously, the first fixing means are constituted by spacers suitable for penetrating into the second cavity of the rim so as to engage between the intermediate ridge and at least one ring sector to act as a wedge and prevent the set of sectors of the ring from moving laterally.
In an embodiment of the invention, the spacers are carried by the sectors of the ring and they are pivotally mounted.
The means for fixing the sectors of the ring on the rim also comprise second means for taking up transverse forces or centrifugal forces tending to cause the sectors to move out from the second cavity of the rim.
The second means for fixing the sectors of the ring on the rim comprise at least one lip provided in the radially inner portion of each sector, and a groove provided in the second cavity of the rim and in which said lip is engaged.
Advantageously, the second means for fixing sectors of the ring on the rim comprise two lips provided in the radially inner portion of each sector, and two grooves formed in the second cavity of the rim and into which the two lips are engaged, respectively.
A runflat system of the present invention presents numerous advantages, and particular mention can be made of the following:
there are no assembly and clamping fasteners between any two consecutive sectors of the ring, thus enabling the structure of the ring to be lightened and minimizing the spacing required between two consecutive sectors of the ring;
the sectors of the ring can be mounted easily around the rim without requiring any special tooling; and
the means for fixing the sectors of the ring on the rim do not require any element to be screwed into the rim, where such elements would weaken the mechanical strength of the rim.